firebase storage download file with download progress

import 'package:path_provider/path_provider.dart';
import 'dart:io';
import 'package:firebase_storage/firebase_storage.dart';

class Download extends StatefulWidget {
  const Download({
    Key? key,
    this.width,
    this.height,
    required this.audiourl,
    required this.name,
    required this.size,
    required this.duration,
    this.docRef,
  }) : super(key: key);

  final double? width;
  final double? height;
  final String audiourl;
  final String name;
  final double size;
  final String duration;
  final DocumentReference? docRef;

  @override
  _DownloadState createState() => _DownloadState();
}

class _DownloadState extends State<Download> {
  int flag = 0; // 0: Initial state, 1: Downloading, 2: Download complete
  double progress = 0.0;

  Future<void> dwonloadAudioSession(String Audiourl, String name) async {
    try {
      setState(() {
        this.flag = 1;
      });
      final ref = FirebaseStorage.instance.ref().child(Audiourl);
      // Get the application document directory
      Directory appDocDir = await getApplicationDocumentsDirectory();
      File downloadToFile = File('${appDocDir.path}/$name.mp3');

      // Start the download
      final downloadTask = ref.writeToFile(downloadToFile);

      // Listen for progress
      await downloadTask.snapshotEvents.listen((taskSnapshot) async {
        switch (taskSnapshot.state) {
          case TaskState.running:
            setState(() {
              this.progress =
                  (taskSnapshot.bytesTransferred / taskSnapshot.totalBytes);
            });
            print("Download is $progress% complete.");
            break;
          case TaskState.paused:
            print("Download paused.");
            break;
          case TaskState.success:
            print("Download complete.");
            setState(() {
              this.flag = 2;

              FFAppState().addToDownloaded(DownloadedStruct(
                  name: widget.name,
                  size: widget.size,
                  data: '${appDocDir.path}/$name.mp3',
                  duration: widget.duration,
                  docRef: widget.docRef));
            });
            break;
          case TaskState.canceled:
            print("Download canceled.");
            setState(() {
              this.flag = 0;
            });

            break;
          case TaskState.error:
            print('task error');
            setState(() {
              this.flag = 0;
            });
            break;
        }
      });
    } catch (e) {
      print('Error occurred while downloading file: $e');
      setState(() {
        flag = 0;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Stack(
        alignment: Alignment.center,
        children: [
          // Show the download icon if flag is 0
          if (flag == 0)
            IconButton(
              icon: Icon(Icons.download),
              alignment: Alignment.center,
              onPressed: () async {
                // Start downloading
                await dwonloadAudioSession(widget.audiourl, widget.name);
              },
            ),
          // Show the progress indicator if flag is 1
          if (flag == 1)
            CircularProgressIndicator(
              value: this.progress, // Show half progress
              backgroundColor: Colors.red,
              valueColor: AlwaysStoppedAnimation<Color>(Colors.blue),
              strokeWidth: 5.0,
              semanticsLabel: 'Downloading',
              semanticsValue: '${this.progress}%', // Value for accessibility
            ),
          // Show the check mark icon if flag is 2
          if (flag == 2)
            Icon(
              Icons.check_circle,
              color: Colors.green,
              size: 48.0,
            ),
        ],
      ),
    );
  }
}